Amino acids (2) Flashcards
Polypeptide
Polypeptide is a polymer of amino acids joined by peptide bonds
Hydrophobic
Hydrophobic means it repels water or lacks an affinity of water
Hydrophilic
Hydrophilic means it is capable of interacting with water through H bonding
Conjugated protein
Conjugated protein is a compound , like haemoglobin, that is made up of a protein molecule and a non protein prosthetic group.
What happens in condensation reaction
In Condensation reactions, OH from carboxylic acid group combines with H of amine on second amino acid. The OH and H are removed and combine to form water, leaving behind a peptide bond between C and N. When 2 amino acids join like this they have formed a dipeptide molecule.
Roles of proteins
Proteins roles are: enzymes, antibodies, hormones, proteins that provide support for muscles and tissues, provide bases for DNA, transport stuff in blood, contractile fibres, actin and myosin.
What happens when proteins don’t fold correctly
Incorrect folding of proteins is responsible for a number of diseases such as Alzheimer’s, Parkinson’s and cystic fibrosis.
Where is the peptide link
The peptide link is where the hydroxide and H formed water so the C double bonded to O which is bonded to N bonded to H
Characteristics of fibrous proteins
Fibrous proteins are long (contain many amino acids)
Amino acid sequence is repetitive and polypeptide chains lie parallel to each other, allowing cross links to form.
No tertiary structure - stay as long chains
E.g keratin in hair, collagen in skin
Insoluble in water
Roles: structural and keratin
Globular protein attributes
Globular proteins fold into a 3D spherical shape.
Irregular non repetitive sequence of amino acid
E.g haemoglobin, insulin and enzymes
Soluble in water
Metabolic role, enzymes plasma proteins
Hydrophobic interactions
Hydrophobic interactions is when r groups that are non polar turn towards the protein, away from water
What is a proteins function dependent on
A proteins function is dependent on its shape, and a mutation may change the composition of a protein so it cannot fold correctly and therefore cannot carry out its function in the cell.
Also, a change in pH may denature enzymes and proteins, changing their shape.
Why does secondary structure form
Secondary structure forms when adjacent C=O and N-H groups interact with each other to form hydrogen bonds resulting in arrangement of polypeptides in alpha helix or beta pleated sheet.
The O of C=O is slightly negative and the H of N-H is slightly positive, which creates electrostatic attraction.
What makes the secondary structure stable
Each H bond is weak but the overall effect of many H bonds makes secondary structure quite stable.
What is structure of an amino acid
Structure of amino acid is:
Has a carboxyl group, containing carbon double bonded to an oxygen and single bonded to a hydroxide group. Amino acid features a central carbon which is single bonded to a hydrogen and an R group. has an amino group consisting of a single N bonded to 2 Cs
